If you use Twitter, Tweetie is a really useful Twitter app for the iPhone and iPod Touch. This app has all the features that active Twitter users need with a super clean interface. There’s not much lacking in this iPhone App, and I believe it's worth every penny of it's $2.99 pricetag.

Sign in with one of your Twitter accounts when you start up the app. I say "one of your Twitter accounts" because this app allows for you to register multiple accounts.After logging in, there are four main buttons (Tweets, Replies, Messages, and Favorites) and a more button for you to delve through. In More you’ll find My Profile, Following, Followers, Trends, and Search.

You can read additional information including customer reviews at the iTunes store:

Hands down, best app I have on my phone. Sseriously, that app is greatnes... I would say it is by far the most used app on my phone, and the only app I have ever moved down to that little bar that holds the four icons in the bottom. It does everything I need it to do, plus a bunch of other stuff that is just cool...

... and let's not forget that supercool 'locating' graphic... makes me feel like a spaceship captain...